Investigation On Brazing Process Of Muti-Clad Aluminum Alloy FA7827

Aluminum alloy heat exchanger is a kind of industrial product widely applied in modern society. With the development of automotive industry, the traditional aluminum heat exchanger using AA 3003 can not meet reliability requirements. So in this project, multi-clad aluminum alloy FA 7827 containing low volume Mg is applied to improve the aluminum alloy heat exchanger reliability.Several root cause which affect FA7827 brazing quality has been analyzed in this study, and also provide the appropriate brazing process parameters here. Discuss the influence of element diffusion, brazing temperature and heat preservation during brazing process. This brazing process is using FA7827 composite plate as raw material, Nitrogen Protect Furnace as basic test equipment, and introducing optics microscope and SEM to observe the quality of brazing connection.From test result, the element Mg diffuse from core alloy to the transition layer and brazing filer metal layer during brazing heating process. Mg's diffusion to clad sheet face will lead to: the decreasing film removing effect of KF- AlF3 flux, the fluidity decreasing of brazing filler on core material surface, and more chance to form the defects, such as no-bonding, pore and slag inclusion at the end-face of lap joint. Using the 10% flux content Cs can advance brazing quality well. The Silicon's diffusion from brazing filler layer to core alloy during brazing heating process lead to form Si deficiency layer in filler layer. It produce different filler metal melting quantity at different brazing temperature, and which also finally affect the brazing quality. During the research to FA7827 composition plate melting erosion, it is discovered that as the brazing temperature increasing and brazing heat preservation time extending, the dissolution of transition layer will be increased, and the tendency of fluid solder's penetration from transition crystal boundary to core material will take place.Through these experiments above, some improvement measures are introduced into FA7827 multi-clad sheet aluminum alloy oil cooler。The temperature of brazing furnace is 605-625-630-645-630℃, conveyer speed is 16HZ。The outer surface temperatures of oil cooler is no more than 603.5℃and keep 3 min in 600℃, The inner temperature of oil cooler is no more than 598℃and keep 4min in 590℃.